Portable power supply



FIG. 1 is a front perspective view of a portable power supply showing my new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a left side elevation view thereof;

FIG. 7 is a front elevation view thereof; and,

FIG. 8 is a rear elevation view thereof.

The broken lines shown represent unclaimed subject matter and form no part of the claimed design. 

CLAIM The ornamental design for a portable power supply, as shown and described. 